The original quote made a comparison between cash and debit/credit cards. Cards are easy to use, too, so clearly "understand" here does not relate to user experience, but to the complexity of the system itself.
That's not true. How to use credit cards very much have an "interface".
- It is open and requires that you protect the numbers on the outside or access to the data on-chip. Many of these security problems have hurt consumers over and over again despite how "easy" cards are to use specifically because those users don't understand the complexity of the card's system.
- It requires you to insert, tap, or swipe it to borrow funds. This interaction is not obvious for a child who has never done this before. It is a learned behavior. And that learned behavior for interfacing with the credit card network with your CC token is complex enough that the US has had significant friction introducing chipped and contactless credit cards over the past years. Because the interface and the UX are there for cards too.
I'm not sure the reason for your distinction between understanding the UX vs the complexity of the system. You can't consider UX without considering complexity... one follows the other necessarily.
